Ionically permeable structures for energy storage devices

ABSTRACT

An electrochemical stack comprising carrier ions, an anode comprising an anode active material layer, a cathode comprising a cathode active material layer, a separator between the anode and the cathode comprising a porous dielectric material and a non-aqueous electrolyte, and an ionically permeable conductor layer located between the separator and an electrode active material layer.

FIELD OF THE INVENTION

The present invention generally relates to structures for use in energystorage devices, to energy storage devices incorporating suchstructures, and to methods for producing such structures and energydevices.

BACKGROUND OF THE INVENTION

Rocking chair or insertion secondary batteries are a type of energystorage device in which carrier ions, such as lithium, sodium orpotassium ions, move between an anode electrode and a cathode electrodethrough an electrolyte. The secondary battery may comprise a singlebattery cell, or two more battery cells that have been electricallycoupled to form the battery, with each battery cell comprising an anodeelectrode, a cathode electrode, and an electrolyte.

In rocking chair battery cells, both the anode and cathode comprisematerials into which a carrier ion inserts and extracts. As a cell isdischarged, carrier ions are extracted from the anode and inserted intothe cathode. As a cell is charged, the reverse process occurs: thecarrier ion is extracted from the cathode and inserted into the anode.

FIG. 1 shows a cross sectional view of an electrochemical stack of anexisting energy storage device, such as a non-aqueous, lithium-ionbattery. The electrochemical stack 1 includes a cathode currentcollector 2, on top of which a cathode layer 3 is assembled. This layeris covered by a microporous separator 4, over which an assembly of ananode current collector 5 and an anode layer 6 are placed. This stack issometimes covered with another separator layer (not shown) above theanode current collector 5, rolled and stuffed into a can, and filledwith a non-aqueous electrolyte to assemble a secondary battery.

The anode and cathode current collectors pool electric current from therespective active electrochemical electrodes and enables transfer of thecurrent to the environment outside the battery. A portion of an anodecurrent collector is in physical contact with the anode active materialwhile a portion of a cathode current collector is in contact with thecathode active material. The current collectors do not participate inthe electrochemical reaction and are therefore restricted to materialsthat are electrochemically stable in the respective electrochemicalpotential ranges for the anode and cathode.

In order for a current collector to bring current to the environmentoutside the battery, it is typically connected to a tab, a tag, apackage feed-through or a housing feed-through, typically collectivelyreferred to as contacts. One end of a contact is connected to one ormore current collectors while the other end passes through the batterypackaging for electrical connection to the environment outside thebattery. The anode contact is connected to the anode current collectorsand the cathode contact is connected to the cathode current collectorsby welding, crimping, or ultrasonic bonding or is glued in place with anelectrically conductive glue.

During a charging process, lithium leaves the cathode layer 3 andtravels through the separator 4 as a lithium ion into the anode layer 6.Depending upon the anode material used, the lithium ion eitherintercalates (e.g., sits in a matrix of an anode material withoutforming an alloy) or forms an alloy. During a discharge process, thelithium leaves the anode layer 6, travels through the separator 4 andpasses through to the cathode layer 3. The current conductors conductelectrons from the battery contacts (not shown) to the electrodes orvice versa.

Existing energy storage devices, such as batteries, fuel cells, andelectrochemical capacitors, typically have two-dimensional laminararchitectures (e.g., planar or spiral-wound laminates) as illustrated inFIG. 1 with a surface area of each laminate being roughly equal to itsgeometrical footprint (ignoring porosity and surface roughness).

Three-dimensional batteries have been proposed in the literature as waysto improve battery capacity and active material utilization. It has beenproposed that a three-dimensional architecture may be used to providehigher surface area and higher energy as compared to a two dimensional,laminar battery architecture. There is a benefit to making athree-dimensional energy storage device due to the increased amount ofenergy that may be obtained out of a small geometric area. See, e.g.,Rust et al., WO2008/089110 and Long et. al, “Three-Dimensional BatteryArchitectures,” Chemical Reviews, (2004), 104, 4463-4492.

New anode and cathode materials have also been proposed as ways toimprove the energy density, safety, charge/discharge rate, and cyclelife of secondary batteries. Some of these new high capacity materials,such as silicon, aluminum, or tin anodes in lithium batteries havesignificant volume expansion that causes disintegration and exfoliationfrom its existing electronic current collector during lithium insertionand extraction. Silicon anodes, for example, have been proposed for useas a replacement for carbonaceous electrodes since silicon anodes havethe capacity to provide significantly greater energy per unit volume ofhost material for lithium in lithium battery applications. See, e.g.,Konishiike et al., U.S. Patent Publication No. 2009/0068567; Kasavajjulaet al., “Nano- and Bulk-Silicon-Based Insertion Anodes for Lithium-IonSecondary Cells,” Journal of Power Sources 163 (2007) 1003-1039. Theformation of lithium silicides when lithium is inserted into the anoderesults in a significant volume change which can lead to crack formationand pulverisation of the anode. As a result, capacity of the battery canbe decreased as the battery is repeatedly discharged and charged.

Monolithic electrodes, i.e., electrodes comprising a mass of electrodematerial that retains its a shape without the use of a binder, have alsobeen proposed as an alternative to improve performance (gravimetric andvolumetric energy density, rates, etc) over particulate electrodes thathave been molded or otherwise formed into a shape and depend upon aconductive agent or binder to retain the shape of an agglomerate of theparticulate material. A monolithic anode, for example, may comprise aunitary mass of silicon (e.g., single crystal silicon, polycrystallinesilicon, amorphous silicon or a combination thereof) or it may comprisean agglomerated particulate mass that has been sintered or otherwisetreated to fuse the anodic material together and remove any binder. Inone such exemplary embodiment, a silicon wafer may be employed as amonolithic anode material for a lithium-ion battery with one side of thewafer coupled to a first cathode element through a separator, while theother side is coupled to a second cathode element opposing it. In sucharrangements, one of the significant technical challenges is the abilityto collect and carry current from the monolithic electrode to theoutside of the battery while efficiently utilizing the space availableinside the battery.

The energy density of conventional batteries may also be increased byreducing inactive component weights and volumes to pack the battery moreefficiently. Current batteries use relatively thick current collectorssince the foils that make up the current collectors are used with aminimum thickness requirement in order to be strong enough to survivethe active material application process. Advantages in performance canbe anticipated if an invention was made in order to separate the currentcollection from processing constraints.

Despite the varied approaches, a need remains for improved batterycapacity and active material utilization.

SUMMARY OF THE INVENTION

Among the various aspects of the present invention is the provision ofionically permeable, electrically conductive structures, referred toherein as ionically permeable conductor layers or more simply as an IPCor IPC layer, for use in energy storage devices such as batteries, fuelcells, and electrochemical capacitors. In certain embodiments, forexample, such layers may more uniformly distribute electrical currentacross the surface of the electrode active material, reduce the inactivecomponent weights and volumes of batteries and other energy storagedevices to pack the devices more efficiently, enable the thickness ofthe electrical contact system to be tailored without being limited byprocessing conditions, and/or provide other significant advantages whenused in combination with particulate electrodes (i.e., composites of aparticulate electrode active material and a conductive agent or otherbinder that have been molded or otherwise formed into a shape and dependupon the conductive agent or other binder to retain their shape) andmonolithic electrodes during battery operation.

Briefly, therefore, one aspect of the present invention is anelectrochemical stack comprising carrier ions, an anode comprising ananode active material layer, a cathode comprising a cathode activematerial layer, a separator between the anode and the cathode comprisinga porous dielectric material and a non-aqueous electrolyte, and anionically permeable conductor layer located between the separator and anelectrode active material layer, the electrode active material being theanode active material layer or the cathode active material layer. Uponapplication of a current to store energy in the electrochemical stack oran applied load to discharge the electrochemical stack: (i) the carrierions travel between the anode and cathode active material layers andthrough the ionically permeable conductor layer and separator as theytravel between the anode active and cathode active material layers, (ii)the anode active material layer, the cathode active material layer, andthe ionically permeable conductor layer each have an electricalconductance, (iii) the anode active material layer, the cathode activematerial layer, the ionically permeable conductor layer and theseparator each have an ionic conductance for the carrier ions, (iv) theratio of the ionic conductance of the ionically permeable conductorlayer to the ionic conductance of the separator is at least 0.5:1, (v)the ratio of the electrical conductance of the ionically permeableconductor layer to the electrical conductance of the electrode activematerial layer is at least 100:1, and (vi) the ratio of the electricalconductance to the ionic conductance of the ionically permeableconductor layer is at least 1,000:1.

Another aspect of the present invention is an energy storage device. Theenergy storage device, such as a secondary battery comprises anelectrochemical stack comprising carrier ions, an anode comprising ananode active material layer, a cathode comprising a cathode activematerial layer, a separator between the anode and the cathode comprisinga porous dielectric material and a non-aqueous electrolyte, and anionically permeable conductor layer located between the separator and anelectrode active material layer, the electrode active material being theanode active material layer or the cathode active material layer. Uponapplication of a current to store energy in the electrochemical stack oran applied load to discharge the electrochemical stack: (i) the carrierions travel between the anode and cathode active material layers andthrough the ionically permeable conductor layer and separator as theytravel between the anode active and cathode active material layers, (ii)the anode active material layer, the cathode active material layer, andthe ionically permeable conductor layer each have an electricalconductance, (iii) the anode active material layer, the cathode activematerial layer, the ionically permeable conductor layer and theseparator each have an ionic conductance for the carrier ions, (iv) theratio of the ionic conductance of the ionically permeable conductorlayer to the ionic conductance of the separator is at least 0.5:1, (v)the ratio of the electrical conductance of the ionically permeableconductor layer to the the electrical conductance of the electrodeactive material layer is at least 100:1, and (vi) the ratio of theelectrical conductance to the ionic conductance of the ionicallypermeable conductor layer is at least 1,000:1.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generic cross-section of an electrochemical stack of anexisting two-dimensional energy storage device such as a lithium ionbattery.

FIG. 2 is a schematic sectional view of an electrochemical stack of anenergy storage device according to a first exemplary embodiment of thepresent invention.

FIG. 3 is a schematic exploded view of a portion of an electrochemicalstack of an energy storage device according to an alternative embodimentof the present invention.

FIG. 4 is a schematic exploded view of a portion of an electrochemicalstack of an energy storage device according to an alternative embodimentof the present invention.

FIG. 5 is a schematic view of a 2-dimensional electrochemical stack ofan energy storage device according to an alternative embodiment of thepresent invention.

FIG. 6 is a schematic view of a 3-dimensional electrochemical stack ofan energy storage device according to an alternative embodiment of thepresent invention.

FIG. 7 is a schematic view of a 3-dimensional electrochemical stack ofan energy storage device according to an alternative embodiment of thepresent invention.

FIG. 8 is a schematic view of an interdigitated 3-dimensionalelectrochemical stack of an energy storage device according to analternative embodiment of the present invention.

FIGS. 9A-9E are schematic illustrations of some shapes into which anodeand cathode structures may be assembled according to certain embodimentsof the present invention.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Among the various aspects of the present invention may be notedionically permeable conductor layers offering particular advantages whenincorporated into electrochemical stacks used in energy storage devicessuch as batteries, capacitors, and fuel cells. The ionically permeableconductor layer may be positioned, for example, between the separatorand the anodically active material layer in an electrochemical stack ofan energy storage device such as a secondary battery, between theseparator and the cathodically active material layer in anelectrochemical stack of an energy storage device such as a secondarybattery, or between the separator and the anodically active materiallayer and between the separator and the cathodically active materiallayer in an electrochemical stack of an energy storage device such as asecondary battery. As carrier ions move between the anodically activematerial and the cathodically active material in an electrochemicalstack, therefore, they pass through an ionically permeable conductorlayer positioned between the separator and the anodically activematerial layer, through an ionically permeable conductor layerpositioned between the separator and the cathodically active materiallayer, or they pass through two ionically permeable conductor layers,one positioned between the separator and the anodically active materiallayer and the other positioned between the separator and thecathodically active material layer. Depending upon the materials ofconstruction of the ionically permeable conductor layer, it may havesome capacity to absorb and release a carrier ion such as lithium; ingeneral, however, it is preferred that this capacity be relativelylimited.

Advantageously, when an ionically permeable conductor layer is on thesurface of the active material of an electrode and between the electrodeand a separator, the ionically permeable conductor layer may facilitatemore uniform carrier ion transport by distributing current from thecurrent collector across the surface of the electrode facing theseparator. This, in turn, may facilitate more uniform insertion andextraction of carrier ions and thereby reduce stress in the activeelectrode material (i.e., the anodically active material and/or thecathodically active material) during cycling; since the ionicallypermeable conductor distributes current to the surface of the electrodefacing the separator, the reactivity of the electrode material forcarrier ions will be the greatest where the carrier ion concentration isthe greatest.

The ionically permeable conductor layer preferably has sufficientelectrical conductance to enable it to serve as a current collector. Inone embodiment, for example, an ionically permeable conductor layer issandwiched between an immediately adjacent anode material layer and animmediately adjacent separator layer of an electrochemical stack, and isthe anode current collector for that anode material layer. By way offurther example, in another embodiment, an ionically permeable conductorlayer is sandwiched between an immediately adjacent cathode materiallayer and an immediately adjacent separator layer of an electrochemicalstack, and is the cathode current collector for that cathode materiallayer. By way of further example, in another embodiment, anelectrochemical stack comprises at least two ionically permeableconductor layers (i) one of the two being sandwiched between animmediately adjacent anode material layer and an immediately adjacentseparator layer and being the anode current collector layer for theimmediately adjacent anode material layer, and (ii) the other of the twobeing sandwiched between an immediately adjacent cathode material layerand an immediately adjacent separator layer and being the cathodecurrent collector layer for the immediately adjacent cathode materiallayer.

In general, the ionically permeable conductor layer is both ionicallyand electrically conductive. Stated differently, the ionically permeableconductor layer has a thickness, an electrical conductivity, and anionic conductivity for carrier ions that facilitates the movement ofcarrier ions between an immediately adjacent active electrode materiallayer one side of the ionically permeable conductor layer and animmediately adjacent separator layer on the other side of the ionicallypermeable conductor layer in an electrochemical stack. On a relativebasis, the ionically permeable conductor layer has an electricalconductance that is greater than its ionic conductance upon applicationof a current to store energy in the electrochemical stack or an appliedload to discharge the electrochemical stack. For example, the ratio ofthe electrical conductance to the ionic conductance (for carrier ions)of the ionically permeable conductor layer will typically be at least1,000:1, respectively, upon application of a current to store energy inthe device or an applied load to discharge the device. By way of furtherexample, in one such embodiment, the ratio of the electrical conductanceto the ionic conductance (for carrier ions) of the ionically permeableconductor layer is at least 5,000:1, respectively, upon application of acurrent to store energy in the device or an applied load to dischargethe device. By way of further example, in one such embodiment, the ratioof the electrical conductance to the ionic conductance (for carrierions) of the ionically permeable conductor layer is at least 10,000:1,respectively, upon application of a current to store energy in thedevice or an applied load to discharge the device. By way of furtherexample, in one such embodiment, the ratio of the electrical conductanceto the ionic conductance (for carrier ions) of the ionically permeableconductor layer is at least 50,000:1, respectively, upon application ofa current to store energy in the device or an applied load to dischargethe device. By way of further example, in one such embodiment, the ratioof the electrical conductance to the ionic conductance (for carrierions) of the ionically permeable conductor layer is at least 100,000:1,respectively, upon application of a current to store energy in thedevice or an applied load to discharge the device.

Upon application of a current to store energy in an electrochemicalstack or an applied load to discharge the electrochemical stack of anenergy storage device, such as when a secondary battery is charging ordischarging, the ionically permeable conductor layer has an ionicconductance that is comparable to the ionic conductance of an adjacentseparator layer. For example, in one embodiment the ionically permeableconductor layer has an ionic conductance (for carrier ions) that is atleast 50% of the ionic conductance of the separator layer (i.e., a ratioof 0.5:1, respectively) upon application of a current to store energy inthe device or an applied load to discharge the device. By way of furtherexample, in some embodiments the ratio of the ionic conductance (forcarrier ions) of the ionically permeable conductor layer to the ionicconductance (for carrier ions) of the separator layer is at least 1:1upon application of a current to store energy in the device or anapplied load to discharge the device. By way of further example, in someembodiments the ratio of the ionic conductance (for carrier ions) of theionically permeable conductor layer to the ionic conductance (forcarrier ions) of the separator layer is at least 1.25:1 upon applicationof a current to store energy in the device or an applied load todischarge the device. By way of further example, in some embodiments theratio of the ionic conductance (for carrier ions) of the ionicallypermeable conductor layer to the ionic conductance (for carrier ions) ofthe separator layer is at least 1.5:1 upon application of a current tostore energy in the device or an applied load to discharge the device.By way of further example, in some embodiments the ratio of the ionicconductance (for carrier ions) of the ionically permeable conductorlayer to the ionic conductance (for carrier ions) of the separator layeris at least 2:1 upon application of a current to store energy in thedevice or an applied load to discharge the device.

The ionically permeable conductor layer also has an electricalconductance that is substantially greater than the electricalconductance of an adjacent electrode active material (La, the anodicallyactive material or the cathodically active material). For example, inone embodiment the ratio of the electrical conductance of the ionicallypermeable conductor layer to the electrical conductance of the electrodeactive material layer is at least 100:1 upon application of a current tostore energy in the electrochemical stack of an energy storage device oran applied load to discharge the electrochemical stack of an energystorage device. By way of further example, in some embodiments the ratioof the electrical conductance of the ionically permeable conductor layerto the electrical conductance of the electrode active material layer isat least 500:1 upon application of a current to store energy in thedevice or an applied load to discharge the device. By way of furtherexample, in some embodiments the ratio of the electrical conductance ofthe ionically permeable conductor layer to the electrical conductance ofthe electrode active material layer is at least 1000:1 upon applicationof a current to store energy in the device or an applied load todischarge the device. By way of further example, in some embodiments theratio of the electrical conductance of the ionically permeable conductorlayer to the electrical conductance of the electrode active materiallayer is at least 5000:1 upon application of a current to store energyin the device or an applied load to discharge the device. By way offurther example, in some embodiments the ratio of the electricalconductance of the ionically permeable conductor layer to the electricalconductance of the electrode active material layer is at least 10,000:1upon application of a current to store energy in the device or anapplied load to discharge the device.

The thickness of ionically permeable conductor layer (i.e., the shortestdistance between the separator and the electrode active material betweenwhich the ionically permeable conductor layer is sandwiched) will dependupon the composition of the layer and the performance specifications forthe electrochemical stack. In general, an ionically permeable conductorlayer will have a thickness of at least about 300 Angstroms. Forexample, in some embodiments it may have a thickness in the range ofabout 300-800 Angstroms. More typically, however, it will have athickness greater than about 0.1 micrometers. In general, an ionicallypermeable conductor layer will have a thickness not greater than about100 micrometers. Thus, for example, in one embodiment, the ionicallypermeable conductor layer will have a thickness in the range of about0.1 to about 10 micrometers. By way of further example, in someembodiments, the ionically permeable conductor layer will have athickness in the range of about 0.1 to about 5 micrometers. By way offurther example, in some embodiments, the ionically permeable conductorlayer will have a thickness in the range of about 0.5 to about 3micrometers. In general, it is preferred that the thickness of theionically permeable conductor layer be approximately uniform. Forexample, in one embodiment it is preferred that the ionically permeableconductor layer have a thickness non-uniformity of less than about 25%wherein thickness non-uniformity is defined as the quantity of themaximum thickness of the layer minus the minimum thickness of the layer,divided by the average layer thickness. In certain embodiments, thethickness variation is even less. For example, in some embodiments theionically permeable conductor layer has a thickness non-uniformity ofless than about 20%. By way of further example, in some embodiments theionically permeable conductor layer has a thickness non-uniformity ofless than about 15%. in some embodiments the ionically permeableconductor layer has a thickness non-uniformity of less than about 10%.

In one preferred embodiment, the ionically permeable conductor layercomprises an electrically conductive component and an ion conductivecomponent that contribute to the ionic permeability and electricalconductivity. Typically, the electrically conductive component willcomprise a continuous electrically conductive material (such as acontinuous metal or metal alloy) in the form of a mesh or patternedsurface, a film, or composite material comprising the continuouselectrically conductive material (such as a continuous metal or metalalloy). Additionally, the ion conductive component will typicallycomprise pores, e.g., interstices of a mesh, spaces between a patternedmetal or metal alloy containing material layer, pores in a metal film,or a solid ion conductor having sufficient diffusivity for carrier ions.In certain embodiments, the ionically permeable conductor layercomprises a deposited porous material, an ion-transporting material, anion-reactive material, a composite material, or a physically porousmaterial. If porous, for example, the ionically permeable conductorlayer may have a void fraction of at least about 0.25. In general,however, the void fraction will typically not exceed about 0.95. Moretypically, when the ionically permeable conductor layer is porous thevoid fraction may be in the range of about 0.25 to about 0.85. In someembodiments, for example, when the ionically permeable conductor layeris porous the void fraction may be in the range of about 0.35 to about0.65

Referring now to FIG. 2, in one embodiment an electrochemical stack 10of the present invention has anodically active material layer 12,ionically permeable conductor layer 14, separator layer 16, cathodicallyactive material layer 18 and cathode current collector layer 20.

Anodically active material layer 12 may comprise an anodically activematerial capable of absorbing and releasing a carrier ion such aslithium, potassium or sodium. Such materials include carbon materialssuch as graphite and soft or hard carbons, or any of a range of metals,semi-metals, alloys, oxides and compounds capable of forming an alloywith lithium. Specific examples of the metals or semi-metals capable ofconstituting the anode material include tin, lead, magnesium, aluminum,boron, gallium, silicon, indium, zirconium, germanium, bismuth, cadmium,antimony, silver, zinc, arsenic, hafnium, yttrium, and palladium. In oneexemplary embodiment, anodically active material layer 12 comprisesaluminum, tin, or silicon, or an oxide thereof, a nitride thereof, afluoride thereof, or other alloy thereof. In another exemplaryembodiment, anodically active material layer 12 comprises silicon or analloy thereof. In each of the embodiments and examples recited in thisparagraph, the anodically active material layer may be monolithic or aparticulate agglomerate.

Ionically permeable conductor layer 14 allows both ionic and electronicconduction and, in a preferred embodiment, ionically permeable conductorlayer also serves as the current collector for the anodically activematerial layer 12. In one such preferred embodiment, ionically permeableconductor layer is the sole anode current collector for anodicallyactive material layer 12. Additionally, or alternatively, in one suchpreferred embodiment the ionically permeable conductor layer has anelectrical conductivity that exceeds the electrical conductivity of theanodically active material layer or any layer in contact with theanodically active material layer (other than another ionically permeableconductor layer on a surface of the anodically active material layer).In general, therefore, it is preferred that the ratio of the ionicconductance (for the carrier ions) of ionically permeable conductorlayer 14 to the ionic conductance (for the carrier ions) of separatorlayer 16 be at least 0.5:1 and in some embodiments at least 1:1, atleast 1.25:1 or even 1.5:1, respectively, upon application of a currentto store energy in the device or an applied load to discharge thedevice. In addition, it is generally preferred that the ratio of theelectrical conductance of ionically permeable conductor layer 14 to theelectrical conductance of anodically active material layer 12 be atleast 100:1 and in some embodiments at least 500:1, at least 1,000:1, atleast 5:000:1 or even 10,000:1, respectively, upon application of acurrent to store energy in the device or an applied load to dischargethe device. It is also generally preferred that the ratio of theelectrical conductance of ionically permeable conductor layer 14 to theionic conductance (for carrier ions, e.g., lithium ions) of ionicallypermeable conductor layer 14 be at least 1,000:1 and in some embodimentsat least 5,000:1, at least 10,000:1, at least 50,000:1 or even at least100,000:1, respectively, upon application of a current to store energyin the device or an applied load to discharge the device.

Separator layer 16 is positioned between ionically permeable conductorlayer 14 and cathodically active material layer 18. Separator layer 16may comprise any of the materials conventionally used as secondarybattery separators including, for example, microporous polyethylenes,polypropylenes, TiO₂, SiO₂, Al₂O₃, and the like (P. Arora and J. Zhang,“Battery Separators” Chemical Reviews 2004, 104, 4419-4462). Suchmaterials may be deposited, for example, by electrophoretic depositionof a particulate separator material, slurry deposition (including spinor spray coating) of a particulate separator material, or sputtercoating of an ionically conductive particulate separator material.Separator layer 38 may have, for example, a thickness (the distanceseparating an adjacent anodic structure and an adjacent cathodicstructure) of about 5 to 100 micrometers and a void fraction of about0.25 to about 0.75.

In operation, the separator may be permeated with a non-aqueouselectrolyte containing any non-aqueous electrolyte that isconventionally used for non-aqueous electrolyte secondary batteries.Typically, the non-aqueous electrolyte comprises a lithium saltdissolved in an organic solvent. Exemplary lithium salts includeinorganic lithium salts such as LiClO₄, LiBF₄, LiPF₆, LiAsF₆, LiCl, andLiBr; and organic lithium salts such as LiB(C₆H₅)₄, LiN(SO₂CF₃)₂,LiN(SO₂CF₃)₃, LiNSO₂CF₃, LiNSO₂CF₅, LiNSO₂C₄F₉, LiNSO₂C₅F₁₁,LiNSO₂C₆F₁₃, and LiNSO₂C₇F₁₅. Exemplary organic solvents to dissolve thelithium salt include cyclic esters, chain esters, cyclic ethers, andchain ethers. Specific examples of the cyclic esters include propylenecarbonate, butylene carbonate, γ-butyrolactone, vinylene carbonate,2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.Specific examples of the chain esters include dimethyl carbonate,diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethylcarbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butylcarbonate, ethyl propyl carbonate, butyl propyl carbonate, alkylpropionates, dialkyl malonates, and alkyl acetates. Specific examples ofthe cyclic ethers include tetrahydrofuran, alkyltetrahydrofurans,dialkyltetrahydrofurans, alkoxytetrahydrofurans,dialkoxytetrahydrofurans, 1,3-dioxolane, alkyl-1,3-dioxolanes, and1,4-dioxolane. Specific examples of the chain ethers include1,2-dimethoxyethane, 1,2-diethoxythane, diethyl ether, ethylene glycoldialkyl ethers, diethylene glycol dialkyl ethers, triethylene glycoldialkyl ethers, and tetraethylene glycol dialkyl ethers.

Cathodically active material layer 18 comprises any of a range ofcathode active materials conventionally used in secondary batteries andother energy storage devices, including mixtures of cathode activematerials. For example, a cathode material such as LiCoO₂,LiNi_(0.5)Mn_(1.5)O₄, Li(Ni_(x)Co_(y)Al₂)O₂, LiFePO₄, Li₂MnO₄, V₂O₅, andmolybdenum oxysulfides are typically used for a lithium-ion battery. Thecathode active material be deposited to form the cathode structure byany of a range of techniques including, for example, electrophoreticdeposition, electrodeposition, co-deposition or slurry deposition. Inone exemplary embodiment, one of the aforementioned cathode activematerials, or a combination thereof, in particulate form iselectrophoretically deposited. In another exemplary embodiment, acathode active material such as V₂O₅ is electrodeposited. In anotherexemplary embodiment, one of the aforementioned cathode activematerials, or a combination thereof, in particulate form is co-depositedin a conductive matrix such as polyaniline. In another exemplaryembodiment, one of the aforementioned cathode active materials, or acombination thereof, in particulate form is slurry deposited.Independent of the method of deposition, the cathode active materiallayer will typically have a thickness between 1 micron and 1 mm. Incertain embodiments, the layer thickness is between 5 microns and 200microns, and in certain embodiments, the layer thickness is between 10microns and 150 microns.

Cathode current collector layer 20 may comprise any of a range of metalsconventionally used for current collectors. For example, in oneembodiment, cathode current collector layer 20 comprises aluminum,carbon, chromium, gold, nickel, NiP, palladium, platinum, rhodium,ruthenium, an alloy of silicon and nickel, titanium, or an alloy of oneor more thereof (see “Current collectors for positive electrodes oflithium-based batteries” by A. H. Whitehead and M. Schreiber, Journal ofthe Electrochemical Society, 152(11) A5105-A2113 (2005)). By way offurther example, in one embodiment, cathode current collector layer 20comprises gold or an alloy thereof such as gold silicide. By way offurther example, in one embodiment, cathode current collector layer 20comprises nickel or an alloy thereof such as nickel silicide.

In an alternative embodiment, the positions of the cathode currentcollector layer and the cathode active material layer are reversedrelative to their positions as depicted in FIG. 2. Stated differently,in some embodiments, the cathode current collector layer is positionedbetween the separator layer and the cathodically active material layer.In such embodiments, the cathode current collector for the immediatelyadjacent cathodically active material layer is also an ionicallypermeable conductor layer. In one such embodiment, the ionicallypermeable conductor (cathode current collector) layer is the solecathode current collector for the cathodically active material layer.Additionally, or alternatively, in one such preferred embodiment theionically permeable conductor (cathode current collector) layer has anelectrical conductivity that exceeds the electrical conductivity of thecathodically active material layer or any layer in contact with thecathodically active material layer (other than another ionicallypermeable conductor layer on a surface of the cathodically activematerial layer).

Referring now to FIG. 3, in one embodiment, the ionically permeableconductor layer comprises a mesh 314 positioned between a separatorlayer 316 and an electrode active material layer 318. The mesh hasinterstices 317 defined by mesh strands 319 of an electricallyconductive material. For example, when electrode active material layer318 is an anodically active material layer, the mesh may comprisestrands 319 of carbon, cobalt, chromium, copper, nickel, titanium, or analloy of one or more thereof. By way of further example, when electrodeactive material layer 318 is a cathodically active material layer, themesh may comprise strands 319 of aluminum, carbon, chromium, gold, NiP,palladium, rhodium, ruthenium, titanium, or an alloy of one or morethereof. In general, the mesh will have a thickness (i.e., the strandsof the mesh have a diameter) of at least about 2 micrometers. In oneexemplary embodiment, the mesh has a thickness of at least about 4micrometers. In another exemplary embodiment, the mesh has a thicknessof at least about 6 micrometers. In another exemplary embodiment, themesh has a thickness of at least about 8 micrometers. In each of theforegoing embodiments, the open area fraction of the mesh (i.e., thefraction of the mesh constituting the interstices 317 between meshstrands 319) is preferably at least 0.5. For example, in each of theforegoing embodiments, the open area fraction of the mesh may be atleast 0.6. By way of further example, in each of the foregoingembodiments, the open area fraction of the mesh may be at least 0.75. Byway of further example, in each of the foregoing embodiments, the openarea fraction of the mesh may be at least 0.8. In general, however, ineach of the foregoing embodiments, the ratio of the average distancebetween the strands of the mesh to the thickness of the electrode activematerial layer is no more than 100:1, respectively. For example, in eachof the foregoing embodiments, the ratio of the average distance betweenthe mesh strands to the thickness of the electrode active material layeris no more than 50:1, respectively. By way of further example, in eachof the foregoing embodiments, the ratio of the average distance betweenthe mesh strands to the thickness of the electrode active material layeris no more than 25:1. Advantageously, one or both ends of the mesh maybe welded or otherwise connected to metal tabs or other connectors toenable collected current to be carried to the environment outside thebattery. As illustrated in FIG. 3, the mesh comprises two sets ofparallel strands with one of sets being oriented perpendicularly and ata different elevation than the other set; in other embodiments, all ofthe strands of the mesh are substantially coplanar.

In those embodiments in which the ionically permeable conductor layercomprises a mesh of a metal or an alloy thereof as previously described,the interstices between the strands of the mesh may be open, they may befilled with a porous material that may be permeated with electrolyte, orthey may contain a nonporous material through which the carrier ions maydiffuse. When filled with a porous material, the porous material willtypically have a void fraction of at least about 0.5, and in someembodiments, the void fraction will be at least 0.6, 0.7 or even atleast about 0.8. Exemplary porous materials include agglomerates of aparticulate ceramic such as SiO₂, Al₂O₃, SiC, or Si₃N₄ and agglomeratesof a particulate polymer such as polyethylene, polypropylene,polymethylmethacrylates and copolymers thereof. Exemplary nonporousmaterials that may be placed in the interstices of the mesh includesolid ion conductors such as Na₃Zr₂Si₂PO₁₂ (NASICON),Li_(2+2x)Zn_(1-x)GeO₄ (LISICON), and lithium phosphorous oxynitride(LiPON).

Referring now to FIG. 4, in one alternative embodiment, the ionicallypermeable conductor layer comprises a mesh 314 of an electricallyconductive material pressed into the separator material. For example,when electrode active material layer 318 is an anodically activematerial layer, the mesh may comprise strands 319 of carbon, cobalt,chromium, copper, nickel, titanium, or an alloy of one or more thereof.By way of further example, when electrode active material layer 318 is acathodically active material layer, the mesh may comprise strands 319 ofaluminum, carbon, chromium, gold, NiP, palladium, rhodium, ruthenium,titanium, or an alloy of one or more thereof. In such embodiments, theionically permeable conductor layer will mesh will have a thickness(i.e., the strands of the mesh have a diameter), an open area fraction(i.e., the interstices between the mesh fibers), a ratio of the averagedistance between the strands of the mesh to the thickness of theelectrode active material layer as previously described for meshes. Inthis embodiment, however, interstices 11 will contain separatormaterial, the ionically permeable conductor layer will have a thicknessX corresponding to the depth to which the mesh is pressed into theseparator material and separator layer 316 will have thickness Y. Forexample, in such embodiments the ionically permeable conductor may havea thickness X of about 1 to about 100 micrometers and separator layer316 will have thickness Y of about 1 to about 100 micrometers.

In one embodiment, the ionically permeable conductor layer comprisesconductive lines deposited or otherwise formed on the surface ofseparator layer or the electrode active material layer. In suchembodiments, the conductive lines may comprises any of the metals (oralloys thereof) previously identified in connection with the meshcomponent. For example, when the ionically permeable conductor layer ispositioned between a separator layer and an anodically active materiallayer, the conductive lines may comprise carbon, cobalt, chromium,copper, nickel, titanium, or an alloy of one or more thereof. When theionically permeable conductor layer is positioned between a separatorlayer and a cathodically active material layer, the conductive lines maycomprise aluminum, carbon, chromium, gold, NiP, palladium, rhodium,ruthenium, an alloy of silicon and nickel, titanium, or an alloy of oneor more thereof. In general, the conductive lines will have a thicknessof at least about 2 micrometers. In one exemplary embodiment, theconductive lines have a thickness of at least about 4 micrometers. Inanother exemplary embodiment, the conductive lines have a thickness ofat least about 6 micrometers. In another exemplary embodiment, theconductive lines have a thickness of at least about 8 micrometers. Ineach of the foregoing embodiments, the ratio of the average distancebetween the conductive lines to the thickness of the electrode activematerial layer is no more than 100:1, respectively. For example, in eachof the foregoing embodiments, the ratio of the average distance betweenthe conductive lines to the thickness of the electrode active materiallayer is no more than 50:1, respectively. By way of further example, ineach of the foregoing embodiments, the ratio of the average distancebetween the conductive lines to the thickness of the electrode activematerial layer is no more than 25:1, respectively. Advantageously, oneor more ends of the conductive lines may be welded or otherwiseconnected to metal tabs or other connectors to enable collected currentto be carried to the environment outside the battery.

In those embodiments in which the ionically permeable conductor layercomprises a conductive line of a metal or an alloy thereof as previouslydescribed, the spaces on the surface of the coated material may be open,they may be filled with a porous material that may be permeated withelectrolyte, or they may contain a nonporous material through which thecarrier ions may diffuse. When filled with a porous material, the porousmaterial will typically have a void fraction of at least about 0.5, andin some embodiments, the void fraction will be at least 0.6, 0.7 or evenat least about 0.8. Exemplary porous materials include agglomerates of aparticulate ceramic such as SiO₂, Al₂O₃, SiC, or Si₃N₄ and agglomeratesof a particulate polymer such as polyethylene, polypropylene,polymethylmethacrylates and copolymers thereof. Exemplary nonporousmaterials that may be placed between the conductive lines include solidion conductors such as Na₃Zr₂Si₂PO₁₂ (NASICON), Li_(2+2x)Zn_(1-x)GeO₄(LISICON), and lithium phosphorous oxynitride (LiPON).

In one alternative embodiment, the ionically permeable conductor layercomprises a porous layer or film such as a porous metal layer. Forexample when electrode active material layer is an anodically activematerial layer, the porous layer may comprise a porous layer of carbon,cobalt, chromium, copper, nickel, titanium, or an alloy of one or morethereof. By way of further example, when electrode active material layeris a cathodically active material layer, the porous layer may comprise aporous layer of aluminum, carbon, chromium, gold, NiP, palladium,rhodium, ruthenium, titanium, or an alloy of one or more thereof.Exemplary deposition techniques for the formation of such porous layersinclude electroless deposition, electro deposition, vacuum depositiontechniques such as sputtering, displacement plating. vapor depositiontechniques such as chemical vapor deposition and physical vapordeposition, co-deposition followed by selective etching, and slurrycoating of metal particles with a binder. In general, it is preferredthat the void fraction of such porous layers be at least 0.25. Forexample, in one embodiment the void fraction of a porous metal layerwill be at least 0.4, at least 0.5, at least 0.6, at least 0.7 and up toabout 0.75. To provide the desired electrical conductance, the layerwill typically have a thickness of at least about 1 micrometer. In someembodiments, the layer will have a thickness of at least 2 micrometers.In some embodiments, the layer will have a thickness of at least 5micrometers. In general, however, the layer will typically have athickness that does not exceed 20 micrometers, and more typically doesnot exceed about 10 micrometers. Optionally, such metal layers or filmsmay contain a binder such as polyvinylidene fluoride (PVDF) or otherpolymeric or ceramic material.

In yet another alternative embodiment, the ionically permeable conductorlayer comprises a metal-filled ion conducting polymer composite film.For example, the ionically permeable conductor layer may comprise anionically conducting film such as polyethylene oxide or gel polymerelectrolytes containing a conductive element such as aluminum, carbon,gold, titanium, rhodium, palladium, chromium, NiP, an alloy of siliconand nickel, or ruthenium, or an alloy thereof. Typically, however, solidion conductors have relatively low ionic conductivity and, thus, thelayers need to be relatively thin to provide the desired ionicconductance. For example, such layers may have a thickness in the rangeof about 0.5 to about 10 micrometers.

Referring again to FIG. 2, in one embodiment, ionically permeableconductor layer 14 comprises a porous layer of a metal or a metal alloy,preferably one which does not form an intermetallic compound withlithium. In this embodiment, for example, ionically permeable conductorlayer 14 may comprise at least one metal selected from the groupconsisting of copper, nickel, and chromium, or an alloy thereof. Forexample, in one such embodiment, ionically permeable conductor layer 14comprises porous copper, porous nickel, a porous alloy of copper ornickel, or a combination thereof. By way of further example, in one suchembodiment, ionically permeable conductor layer 14 comprises porouscopper or an alloy thereof such as porous copper silicide. By way offurther example, in one such embodiment, ionically permeable conductorlayer 14 comprises porous nickel or a porous alloy thereof such asporous nickel silicide. In each of the foregoing embodiments recited inthis paragraph, the thickness of the ionically permeable conductor layer14 (La, the shortest distance between anodically active material layer12 and separator layer 16, as illustrated) will generally be at leastabout 0.1 micrometers, and typically in the range of about 0.1 to 10micrometers. In each of the foregoing embodiments recited in thisparagraph, the ionically permeable conductor layer 14 may be porous witha void fraction of in the range of about 0.25 to about 0.85 and, incertain embodiments, in the range of about 0.35 to about 0.65.

In one preferred embodiment, ionically permeable conductor layer 14 isformed by a process comprising a displacement plating step. In thisembodiment, anodically active material layer 12 is silicon and the layeris contacted with a solution comprising ions of a metal and adissolution component for dissolving part of the silicon. The silicon isdissolved, the metal in solution is reduced by electrons provided by thedissolution of the silicon, and the metal is deposited on the anodicallyactive material layer, and annealing to form a metal-silicon alloylayer. The “dissolution component” refers to a constituent that promotesdissolution of the semiconductor material. Dissolution componentsinclude fluoride, chloride, peroxide, hydroxide, permanganate, etc.Preferred dissolution components are fluoride and hydroxide. Mostpreferred dissolution component is fluoride. The metal may be any of theaforementioned metals, with nickel and copper being preferred.Advantageously, the resulting layer will be porous, having a voidfraction of about 0.15 to about 0.85. Additionally, the thickness of theresulting ionically permeable conductor layer can be controlled to bebetween about 100 nanometers and 3 micrometers; if desired, thickerlayers can be formed.

Anodically active material layer 12 may comprise an anodically activematerial capable of absorbing and releasing a carrier ion such aslithium, potassium or sodium. Such materials include carbon materialssuch as graphite and carbides, or any of a range of metals, semi-metals,alloys, oxides and compounds capable of forming an alloy with lithium.Specific examples of the metals or semi-metals capable of constitutingthe anode material include tin, lead, magnesium, aluminum, boron,gallium, silicon, indium, zirconium, germanium, bismuth, cadmium,antimony, silver, zinc, arsenic, hafnium, yttrium, and palladium. In oneexemplary embodiment, anodically active material layer 12 comprisesaluminum, tin, or silicon, or an oxide thereof, a nitride thereof, afluoride thereof, or other alloy thereof. In another exemplaryembodiment, anodically active material layer 12 comprises silicon or analloy thereof.

Referring now to FIG. 5, in one embodiment an electrochemical stack 510comprises electrochemical cathode current collector layers 520, cathodelayers 518, separator layers 516, ionically permeable conductor layers514 and anode layers 512 are arranged in a 2-dimensional format. Cathodecurrent collector layers 520 are electrically connected to the cathodecontact (not shown) and ionically permeable conductor layers 514 areelectrically connected to the anode contact (not shown). For ease ofillustration, only two anode layers 512 and only three cathode layers518 are depicted in FIG. 5; in practice, however, an electrochemicalstack will typically comprise an alternating series of anode and cathodelayers, with the number of anode and cathode layers per stack dependingupon the application.

Referring now to FIG. 6, in one embodiment an electrochemical stack 610comprises reference plane 601 and backbones 603 projecting generallyvertically from reference plane 601. The cathodic elements ofelectrochemical stack 610 comprise cathode current collector layers 620and cathode active material layers 618. The anodic elements ofelectrochemical stack 610 comprise anodic active material layers 612 andionically permeable conductor layer 614 which also serves as an anodecurrent collector layer. Preferably, ionically permeable conductor layer614 has a thickness at the top of backbone 603, i.e., the surface ofbackbone distal to reference plane 601, that is greater than thethickness of ionically permeable layer on the lateral sides of backbone603 (the surfaces between the top and reference plane 601); for example,in one embodiment, the thickness at the top of the backbone is 110% to2,000% of the thickness of the ionically permeable conductor on thelateral surfaces. By way of further example, in one embodiment thethickness at the top of the backbone is 200% to 1,000% of the thicknessof the ionically permeable conductor on the lateral surfaces. Separatorlayer 616 is between ionically permeable conductor layer 614 andcathodically active material layers 618. Cathode current collectorlayers 620 are electrically connected to the cathode contact (not shown)and ionically permeable conductor layer 614 is electrically connected tothe anode contact (not shown). For ease of illustration, only one anodebackbone and only two cathode backbones are depicted in FIG. 6; inpractice, however, an electrochemical stack will typically comprise analternating series of anode and cathode backbones, with the number ofper stack depending upon the application.

Backbones 603 provide mechanical stability for anodically activematerial layer 612 and cathodically active material layers 618. Ingeneral, the backbones will have a thickness (measured in a directionparallel to reference plane 601) of at least 1 micrometer but generallynot in excess of 100 micrometers. For example, in one embodiment,backbones 603 will have a thickness of about 1 to about 50 micrometers.In general, backbones 603 will have a height (as measured in a directionperpendicular to reference plane 601) of at least about 50 micrometers,more typically at least about 100 micrometers. In general, however,backbones 603 will typically have a height of no more than about 10,000micrometers, and more typically no more than about 5,000 micrometers. Byway of example, in one embodiment, backbones 603 will have a thicknessof about 5 to about 50 micrometers and a height of about 50 to about5,000 micrometers. By way of further example, in one embodiment,backbones 603 will have a thickness of about 5 to about 20 micrometersand a height of about 100 to about 1,000 micrometers. By way of furtherexample, in one embodiment, backbones 603 will have a thickness of about5 to about 20 micrometers and a height of about 100 to about 2,000micrometers.

Backbones 603 may comprise any material that may be shaped, such asmetals, semiconductors, organics, ceramics, and glasses. Presentlypreferred materials include semiconductor materials such as silicon andgermanium. Alternatively, however, carbon-based organic materials ormetals, such as aluminum, copper, nickel, cobalt, titanium, andtungsten, may also be incorporated into anode backbone structures. Inone exemplary embodiment, backbones 603 comprise silicon. The silicon,for example, may be single crystal silicon, polycrystalline silicon oramorphous silicon.

In one embodiment, anodically active material layers 612 aremicrostructured to provide a significant void volume fraction toaccommodate volume expansion and contraction as lithium ions (or othercarrier ions) are incorporated into or leave anodically active materiallayers 612 during charging and discharging processes. In general, thevoid volume fraction of the anodically active material layer is at least0.1. Typically, however, the void volume fraction of the anodicallyactive material layer is not greater than 0.8. For example, in oneembodiment, the void volume fraction of the anodically active materiallayer is about 0.15 to about 0.75. By way of the further example, in oneembodiment, the void volume fraction of the anodically active materiallayer is about 0.2 to about 0.7. By way of the further example, in oneembodiment, the void volume fraction of the anodically active materiallayer is about 0.25 to about 0.6.

Depending upon the composition of the microstructured anodically activematerial layer and the method of its formation, the microstructuredanodically active material layers may comprise macroporous, microporousor mesoporous material layers or a combination thereof such as acombination of microporous and mesoporous or a combination of mesoporousand macroporous. Microporous material is typically characterized by apore dimension of less than 10 nm, a wall dimension of less than 10 nm,a pore depth of 1-50 micrometers, and a pore morphology that isgenerally characterized by a “spongy” and irregular appearance, wallsthat are not smooth and branched pores. Mesoporous material is typicallycharacterized by a pore dimension of 10-50 nm, a wall dimension of 10-50nm, a pore depth of 1-100 micrometers, and a pore morphology that isgenerally characterized by branched pores that are somewhat well definedor dendritic pores. Macroporous material is typically characterized by apore dimension of greater than 50 nm, a wall dimension of greater than50 nm, a pore depth of 1-500 micrometers, and a pore morphology that maybe varied, straight, branched or dendritic, and smooth or rough-walled.Additionally, the void volume may comprise open or closed voids, or acombination thereof. In one embodiment, the void volume comprises openvoids, that is, the anodically active material layer contains voidshaving openings at the surface of the anodically active material layer,the void openings facing the separator and the cathodically activematerial and through which lithium ions (or other carrier ions) canenter or leave the anodically active material layer; for example,lithium ions may enter the anodically active material layer through thevoid openings after leaving the cathodically active material andtraveling to the anodically active material. In another embodiment, thevoid volume is closed, meaning that the anodically active material layercontains voids that are enclosed by anodically active material. Ingeneral, open voids can provide greater interfacial surface area for thecarrier ions whereas closed voids tend to be less susceptible to solidelectrolyte interface (“SEI”) while each provides room for expansion ofthe anodically active material layer upon the entry of carrier ions. Incertain embodiments, therefore, it is preferred that anodically activematerial layer comprise a combination of open and closed voids.

Anodically active material layers 612 comprise any of the anodicallyactive materials previously described herein that are capable ofabsorbing and releasing a carrier ion such as lithium. Such materialsinclude carbon materials such as graphite and carbides, or any of arange of metals, semi-metals, alloys, oxides and compounds capable offorming an alloy with lithium. Specific examples of the metals orsemi-metals capable of constituting the anode material include tin,lead, magnesium, aluminum, boron, gallium, silicon, indium, zirconium,germanium, bismuth, cadmium, antimony, gold, silver, zinc, arsenic,hafnium, yttrium, and palladium. In one exemplary embodiment, anodicallyactive material layers 612 comprise aluminum, tin, or silicon, or anoxide thereof, a nitride thereof, a fluoride thereof, or other alloythereof. In another exemplary embodiment, anodically active materiallayers 612 comprise microstructured silicon or an alloy thereof. In oneparticularly preferred embodiment, anodically active material layers 612comprise porous silicon or an alloy thereof, fibers (e.g., nanowires) ofsilicon or an alloy thereof, a combination of porous silicon or an alloythereof and fibers (e.g., nanowires) of silicon or an alloy thereof, orother forms of microstructured silicon or an alloy thereof having a voidvolume fraction of at least 0.1. In each of the embodiments and examplesrecited in this paragraph and elsewhere in this patent application, theanodically active material layer may be monolithic or a particulateagglomerate.

In general, anodically active material layers 612 will have thicknesses(measured in a direction parallel to the surface of reference plane 601)of at least 1 micrometer. Typically, however, anodically active materiallayers 612 will each have a thickness that does not exceed 200micrometers. For example, in one embodiment, anodically active materiallayers 612 will have a thickness of about 1 to about 100 micrometers. Byway of further example, in one embodiment, anodically active materiallayers 612 will have a thickness of about 2 to about 75 micrometers. Byway of further example, in one embodiment, anodically active materiallayers 612 have a thickness of about 10 to about 100 micrometers. By wayof further example, in one embodiment, anodically active material layers612 have a thickness of about 5 to about 50 micrometers. By way offurther example, in one such embodiment, anodically active materiallayers 612 have a thickness of about 20 to about 50 micrometers andcontain microstructured silicon and/or an alloy thereof such as nickelsilicide. By way of further example, in one such embodiment, anodicallyactive material layers 612 have a thickness of about 1 to about 100micrometers and contain microstructured silicon and/or an alloy thereofsuch as nickel silicide.

Referring now to FIG. 7, in one embodiment an electrochemical stack 610comprises reference plane 601 and backbones 603 projecting generallyvertically from reference plane 601. The cathodic elements ofelectrochemical stack 610 comprise cathode current collector layers 620and cathode active material layers 618. The anodic elements ofelectrochemical stack 610 comprise anodic active material layers 612 andionically permeable conductor layer 614 which also serves as an anodecurrent collector layer. Separator layer 616 is between ionicallypermeable conductor layer 614 and cathodically active material layers618. In this embodiment, anodic active material layer 612 is on the topand lateral surfaces of backbone 603 and cathodic active material 618 isproximate the top and lateral surfaces of backbone 603. As a result,during charging and discharging of an energy storage device comprisingelectrochemical stack 610, carrier ions are simultaneously moving in twodirections relative to reference plane 601: carrier ions are moving in adirection generally parallel to reference plane 601 (to enter or leaveanodically active material 612 on the lateral surface of backbone 603)and in a direction generally orthogonal to the reference plane 601 (toenter or leave anodically active material 612 at the top surface ofbackbone 603). Cathode current collector layers 620 are electricallyconnected to the cathode contact (not shown) and ionically permeableconductor layer 614 is electrically connected to the anode contact (notshown). For ease of illustration, only one anode backbone and only twocathode backbones are depicted in FIG. 7; in practice, however, anelectrochemical stack will typically comprise an alternating series ofanode and cathode backbones, with the number per stack depending uponthe application.

Referring now to FIG. 8, in one embodiment an electrochemical stack 710comprises interdigitated anodically active material layers 712 andcathodically material layers 718. The cathodic elements ofelectrochemical stack 710 further comprise cathode current collectorlayer 720 and the anodic elements of the electrochemical stack compriseionically permeable conductor layer 714 which functions as the anodecurrent collector. Separator 716 is between ionically permeableconductor layer 714 and cathodically active material layer 718. Supportlayers 705, 707 provide mechanical support for interdigitated anodicallyactive material layers 712. Although not shown in FIG. 8, in oneembodiment, anodically active material layers 712 and cathodicallyactive material layers 718 and may be supported by backbones, asillustrated in and described in connection with FIG. 6.

Some examples of other three-dimensional architectures that are capableof use with certain embodiments of the present invention are illustratedin FIGS. 9A-9E. Anode structures 24 and cathode structures 26 projectfrom a reference plane, in this embodiment, the planar surface of base22, and alternate in periodic fashion. For example, when anodestructures 24 are in the shape of pillars (FIG. 9A), the microstructuredanodically active material layer extends at least partially, andpreferably fully about the circumference of the lateral surface. By wayof further example, when anode structures 24 have two (or more) lateralsurfaces as illustrated, for example, in FIGS. 9B-9E, the anodicallyactive material layer at least partially covers, and preferably fullycovers, at least one of the lateral surfaces. Additionally, each of themicrostructured anodically active material layers in the population hasa height (measured in a direction perpendicular to base 22) and thelayers are disposed such that the distance between at least two of thelayers of the population, e.g., layers 30A and 30B, measured in adirection that is substantially parallel to the planar surface of base22 is greater than the maximum height of any of the layers in thepopulation. For example, in one embodiment, the distance between atleast two of the layers of the population, e.g., layers 30A and 30B, isgreater than the maximum height of any of the layers in the populationby a factor of at least 2, and in some embodiments substantially more,e.g., by a factor of at least 5 or even 10. By way of further example,in one embodiment, the distance between a majority of the layers of thepopulation is greater than the maximum height of any of the layers inthe population by a factor of at least 2, and in some embodimentssubstantially more, e.g., by a factor of at least 5 or even 10.

FIG. 9A shows a three-dimensional assembly with anode structures 24 andcathode structures 26 in the shape of pillars. Each of the pillarscomprises a backbone having a lateral surface (not shown) projectingvertically from base 22. The lateral surface of each of the backbonessupports an anodically active material layer 30 and the layers 30 aredisposed such that the distance between at least two of the layers ofthe population, e.g., layers 30A and 30B, is greater than the maximumheight of any of the layers in the population.

FIG. 9B shows a three-dimensional assembly with cathode structures 26and anode structures 24 in the shape of plates. Each of the platescomprises a backbone having a lateral surface (not shown) projectingvertically from base 22. The lateral surface of each of the backbonessupports an anodically active material layer 30 and the layers 30 aredisposed such that the distance between at least two of the layers ofthe population, e.g., layers 30A and 30B, is greater than the maximumheight of any of the layers in the population.

FIG. 9C shows a three-dimensional assembly with cathode structures 26and anode structures 24 in the shape of concentric circles. Each of theconcentric circles comprises a backbone having a lateral surface (notshown) projecting vertically from base 22. The lateral surface of eachof the backbones supports an anodically active material layer 30 and thelayers 30 are disposed such that the distance between at least two ofthe layers of the population, e.g., layers 30A and 30B, is greater thanthe maximum height of any of the layers in the population.

FIG. 9D shows a three-dimensional assembly with cathode structures 26and anode structures 24 in the shape of waves. Each of the wavescomprises a backbone having a lateral surface (not shown) projectingvertically from base 22. The lateral surface of each of the backbonessupports an anodically active material layer 30 and the layers 30 aredisposed such that the distance between at least two of the layers ofthe population, e.g., layers 30A and 30B, is greater than the maximumheight of any of the layers in the population.

FIG. 9E shows a three-dimensional assembly with cathode structures 26and anode structures 24 in a honeycomb pattern. The cathode structures26 are in the shape of pillars at the center of each unit cell of thehoneycomb structure and the walls of each unit cell of the honeycombstructure comprise an interconnected backbone network (system) havinglateral surfaces (not shown) projecting vertically from base 22. Thelateral surfaces of the backbone network (system) support anodicallyactive material layers 30 and the layers 30 are disposed such that thedistance between at least two of the layers of the population, e.g.,layers 30A and 30B, is greater than the maximum height of any of thelayers in the population. In an alternative embodiment, thethree-dimensional assembly is a honeycomb structure, but the relativepositions of the anode structures and cathode structures reversedrelative to the embodiment depicted in FIG. 9E, i.e., in the alternativeembodiment, the anode structures are in the shape of pillars (havinglateral surfaces supporting anodically active material layers) and thewalls of each unit cell comprise cathodically active material.

In one embodiment, a three-dimensional secondary battery comprises oneor more three-dimensional electrochemical stacks, such as one of thethree-dimensional architectures illustrated in FIGS. 6-8, a batteryenclosure, and tabs for electrically connecting the electrochemicalstacks to an external energy supply or consumer. For lithium ionbatteries for portable electronics such as mobile phones and computers,for example, battery enclosure may be a pouch or other conventionalbattery enclosure.

The following non-limiting examples are provided to further illustratethe present invention.

EXAMPLES Example 1 Formation of an IPC Layer on a Monolithic Anode

A Silicon substrate 500 μm thick is used as the starting material. Thesilicon substrate is cleaned and polished in 20% KOH solution at 65 C.for 3 minutes to clean the silicon surface. This sample is immersed in500 milliliters of solution containing 0.1 M NiSO₄.6H₂O and 5M NH₄F. ThepH of the solution was maintained at 8.5 and the operating temperaturewas 85 C. The deposition time of the sample was 3 minutes. The samplewas subsequently rinsed in DI water for 5 minutes and dried at 80 C. inair. Subsequently, the sample was annealed to a temperature of 550° C.for 20 minutes (including heating and cooling time) to form the silicidecontaining IPC layer.

Example 1A Formation of an IPC Layer on a Monolithic Anode

A Silicon substrate 500 μm thick is used as the starting material. Thesilicon substrate is cleaned and polished in 20% KOH solution at 65 C.for 3 minutes to clean the silicon surface. This sample is immersed in500 milliliters of solution containing 0.1 M NiSO₄.6H₂O and 5M NH₄F. ThepH of the solution was maintained at 8.5 and the operating temperaturewas 85° C. The deposition time of the sample was 3 minutes. The samplewas subsequently rinsed in DI water for 5 minutes and dried at 80° C. inair. Subsequently, the sample was annealed to a temperature of 550° C.for 20 minutes (including heating and cooling time) to form the silicidecontaining IPC layer. The excess Ni that did not form the silicide wasselectively etched using a solution of 10% H₂O₂ and 10% H₂SO₄ for 10minutes at 75° C.

Example 1B Formation of an IPC Layer on a Monolithic Anode

A Silicon substrate 500 μm thick is used as the starting material. Thesilicon substrate is cleaned and polished in 20% KOH solution at 65° C.for 3 minutes to clean the silicon surface. This sample is immersed in500 milliliters of solution containing 0.1 M NiSO₄.6H₂O and 5M NH₄F. ThepH of the solution was maintained at 8.5 and the operating temperaturewas 85° C. The deposition time of the sample was 3 minutes. The samplewas subsequently rinsed in DI water for 5 minutes and dried at 80° C. inair. Subsequently, the sample was annealed to a temperature of 300° C.for 5 minutes (including heating and cooling time) to improve theadhesion of deposited Ni to silicon. Since the deposit was based on adisplacement nickel deposition, the Ni layer was porous and was able toallow the Lithium transport when assembled as an anode in a lithiumbattery.

Example 2 Formation of Battery with the IPC Layer from Example 1

The silicon substrate with the Ni+NiSi IPC layer from Example 1 was tobe used as the anode material in the lithium ion battery. An overhangingedge of the silicon piece was wirebonded with Cu wire in order toprovide the means for electrical connection to the outside of thebattery package, commonly referred to as the tab. The wirebonding inthis case was done on either side of the anode surface; however, it ispossible to collect the current from one side alone if the IPC layer iscoated on the sides of the anode piece as well. This wirebonded Si piecewas wrapped with a 25 μm thick separator over the sample, and aconventional single sided coated and calendared cathode foil was used oneither side of the anode/separator combination. Each cathode foil wastabbed using an aluminum tab. The assembly was then covered with aconventional lithium battery pouch material, filled with electrolyte,and sealed with the tab connections from the cathode and anodeprotruding through the seal to form the positive and negative electrodeconnections for charge/discharge of the battery.

Example 3 Formation of Battery with the IPC Layer from Example 1

The silicon substrate with the Ni+NiSi IPC layer from Example 1 was tobe used as the anode material in the lithium ion battery. A copper mesh25 μm thick was dipped in a solution of 2 wt % PVDF and 4 wt % carbonblack. One mesh was laid over each surface of the anode, pressed, andheated to 120° C. for 10 min in a pressed state to form an electricalconnection between the mesh and the porous Ni layer above the anode fromExample 1. The overhangs of the mesh were cut off using a mesh cutter onthree sides while leaving one side overhanging. This mesh was thenwelded to a Ni tab, which served as the connection to the environmentoutside of the device. The anode+IPC current collector was wrapped witha 25 μm thick separator over the sample, and a conventional single sidedcoated and calendared cathode foil was used on either side of theanode/separator combination. Each cathode foil was tabbed using analuminum tab. The assembly was then covered with a conventional lithiumbattery pouch material, filled with electrolyte, and sealed with the tabconnections from the cathode and anode protruding through the seal toform the positive and negative electrode connections forcharge/discharge of the battery.

Example 4 Formation of an IPC Layer on a Particulate Anode andParticulate Cathode

A 10 μm thick mylar foil was used as a substrate. A solution of MCMBgraphite particles (10 μm average particle size), carbon black, andpolyvinylidene difluoride (PVDF) with a ratio of 90:5:5 by weight weremixed in n-Methyl Pyrollidone to form a slurry. This slurry was coatedon the Mylar foil and dried with forced convection before sendingthrough a 20 ton calendar roll to a target thickness of 120 μm. Asimilar process was used with LiCoO₂, graphite, carbon black, andpolyvinylidene difluoride (PVDF) in a ratio of 90:2.5:2.5:5 by weight.This slurry was coated on the Mylar foil and dried with forcedconvection before sending through a 20 ton calendar roll to a targetthickness of 100 μm. A copper mesh 25 μm thick was dipped in a solutionof 2 wt % PVDF and 4 wt % carbon black. The mesh was laid over thesurface of the anode, pressed, and heated to 120° C. for 10 min in apressed state to form an electrical connection between the mesh and theanode material coated Mylar film. The overhangs of the mesh were cut offusing a mesh cutter on three sides while leaving one side overhanging.This mesh was then welded to a Ni tab, which served as the connection tothe environment outside of the device. An aluminum mesh 20 μm thick wasdipped in a solution of 2 wt % PVDF and 4 wt % carbon black. The meshwas laid over the surface of the cathode, pressed, and heated to 120° C.for 10 min in a pressed state to form an electrical connection betweenthe mesh and the cathode material coated Mylar film. The overhangs ofthe mesh were cut off using a mesh cutter on three sides while leavingone side overhanging. This mesh was then welded to a Al tab, whichserved as the connection to the environment outside of the device. Theanode+ IPC, and the cathode+ IPC layers were assembled together with a25 μm polyolefin separator material in between to act as the separator.The assembly was then covered with a conventional lithium battery pouchmaterial, filled with electrolyte, and sealed with the tab connectionsfrom the cathode and anode protruding through the seal to form thepositive and negative electrode connections for charge/discharge of thebattery.

Example 5 Formation of an IPC Layer on a Particulate Anode

A 10 μm thick mylar foil was used as a substrate. A solution of MCMBgraphite particles (10 μm average particle size), carbon black, andpolyvinylidene difluoride (PVDF) with a ratio of 90:5:5 by weight weremixed in n-Methyl Pyrollidone to form a slurry. This slurry was coatedon the Mylar foil and dried with forced convection before sendingthrough a 20 ton calendar roll to a target thickness of 120 μm. Asimilar process was used with LiCoO₂, graphite, carbon black, andpolyvinylidene difluoride (PVDF) in a ratio of 90:2.5:2.5:5 by weight.This slurry was coated on the Mylar foil and dried with forcedconvection before sending through a 20 ton calendar roll to a targetthickness of 100 μm. A slurry consisting of 90% by weight copperparticles, 2-5 μm in diameter, 8% Graphite, and 2% PVDF in NMP wascoated on top of the anode and dried using forced convection methods.The resultant film was again sent through a 20 ton calendar roll toachieve a target thickness of 130 μm, which accounts for 10 μm thicknessof the IPC layer. A nickel tab was attached to one of the edges of theelectrode with a graphite based conductive epoxy to provide electricalconnections to the environment outside of the device. This anode+ IPClayer was assembled together with a 25 μm polyolefin separator materialin between to act as the separator, and a conventional cathode materialwith an Aluminum tab connection. The assembly was then covered with aconventional lithium battery pouch material, filled with electrolyte,and sealed with the tab connections from the cathode and anodeprotruding through the seal to form the positive and negative electrodeconnections for charge/discharge of the battery.

Example 6 Formation of a Sintered Particulate Electrode with IPC Layer

A sample of 2 grams of silicon particulates in powder form (−325 mesh)was immersed for 30 seconds in 50 milliliters of a solution 0.1 MNiSO₄.6H₂O and 5M NH₄F. The pH of the solution was maintained at 8.5 andthe operating temperature was 85° C. Deposition was done with the powderon top of a filter paper assembled in a Buchner funnel. Vigorous bubbleswere observed during deposition indicating the nickel displacementreaction. The solution was drained out through the application of vacuumin the Buchner funnel. The sample was rinsed with DI water for 10minutes to remove trace salt contamination. The powder was harvested anddried at 80° C. in air for 12 hours. Separately, a 25 μm thick nickelmesh was hot-pressed to a Mylar foil at 150° C. so that approximately5-10 μm of the 25 μm mesh was embedded into the Mylar foil. Thedisplacement nickel coated particles are dispersed in an aqueoussolution containing carboxymethylcellulose and coated onto themesh/mylar substrate. The coated mesh is dried to remove water. Oncedry, the Mylar film is peeled from the back end, leaving the mesh andcoated anode slurry behind. This mixture is heated to 850° C. in anargon atmosphere to sinter the nickel silicide coated particles to eachother and to the nickel mesh. The resultant sintered electrode is thenused as the anode material with the nickel mesh surface having beenassembled closest to the separator interface.

Example 7 Ion-Conductive Layer+ Patterned Metal as IPC

A 25 μm thick Mylar foil was used as a substrate, on top of which a 1 μmthick film of amorphous silicon anode material was sputter deposited.The sample was then coated with a 10 μm thick photoresist, which wassubsequently line-patterned with a landing pad. This sample was thendeposited with 2 μm of copper both in the trenches and on thephotoresist to form a full film. Subsequently, the resist was strippedin hot NMP solution to remove and undercut the Cu metal on top of thephotoresist pattern leaving behind the line patterned sample. The samplewas then sputter deposited with a 0.25 μm thick film of Lithiumphosphorus oxynitride (LIPON) by sputter coating from a lithiumphosphate target in the presence of nitrogen. This combination was usedas an anode in a lithium-ion battery.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above articles, compositions andmethods without departing from the scope of the invention, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:
 1. An electrochemical stack comprising carrier ions,an anode comprising an anode active material layer, a cathode comprisinga cathode active material layer, a separator between the anode and thecathode comprising a porous dielectric material and a non-aqueouselectrolyte, and an ionically permeable conductor layer located betweenthe separator and an electrode active material layer, the electrodeactive material being the anode active material layer or the cathodeactive material layer so wherein upon application of a current to storeenergy in the electrochemical stack or an applied load to discharge theelectrochemical stack: (i) the carrier ions travel between the anode andcathode active material layers and through the ionically permeableconductor layer and separator as they travel between the anode activeand cathode active material layers, (ii) the anode active materiallayer, the cathode active material layer, and the ionically permeableconductor layer each have an electrical conductance, (iii) the anodeactive material layer, the cathode active material layer, the ionicallypermeable conductor layer and the separator each have an ionicconductance for the carrier ions, (iv) the ratio of the ionicconductance of the ionically permeable conductor layer to the ionicconductance of the separator is at least 0.5:1, (v) the ratio of theelectrical conductance of the ionically permeable conductor layer to theelectrical conductance of the electrode active material layer is atleast 100:1, and (vi) the ratio of the electrical conductance to theionic conductance of the ionically permeable conductor layer is at least1,000:1.
 2. The electrochemical stack of claim 1 wherein the ionicallypermeable conductor layer is between the separator and the anode activematerial layer.
 3. The electrochemical stack of claim 1 wherein theionically permeable conductor layer is between the separator and thecathode active material layer.
 4. The electrochemical stack of claim 1wherein the electrochemical stack comprises two ionically permeableconductor layers, one of the ionically permeable conductor layers isbetween the separator and the anode, and the other of the ionicallypermeable conductor layers is between the separator and the cathode. 5.The electrochemical stack of claim 1 wherein the anode comprises ananode current collector, the cathode comprises a cathode currentcollector, and the ionically permeable conductor layer comprises theanode current collector.
 6. The electrochemical stack of claim 1 whereinthe anode comprises an anode current collector, the cathode comprises acathode current collector, and the ionically permeable conductor layercomprises the cathode current collector.
 7. The electrochemical stack ofclaim 1 wherein the anode comprises an anode current collector, thecathode comprises a cathode current collector, and the electrochemicalstack comprises two ionically permeable conductor layers, one of theionically permeable conductor layers being between the separator and theanode active material and comprising the anode current collector and theother of the ionically permeable conductor layers being between theseparator and the cathode active material and comprising the cathodecurrent collector.
 8. The electrochemical stack of claim 1 wherein theionically permeable conductor layer comprises a porous material and thenon-aqueous electrolyte, and the porous material is selected from thegroup consisting, of porous metals and porous metal alloys.
 11. Theelectrochemical stack of claim 1 wherein the ionically permeableconductor layer comprises a mesh or conductive lines, the mesh orconductive lines comprising a metal or alloy thereof.
 12. Theelectrochemical stack of claim 1 wherein the ionically permeableconductor layer comprises a solid ion conductor.
 13. The electrochemicalstack of claim 1 wherein the ionically permeable conductor layer porouscopper, porous nickel, a porous alloy of copper or nickel, or acombination thereof having a void fraction in the range of about 0.25 toabout 0.85 and a thickness in the range of about 300 Angstroms to about3 micrometers.
 14. The electrochemical stack of each of claims 1-13wherein the anodically active material layer comprises silicon or analloy thereof.
 15. The electrochemical stack of each of claim 14 whereinthe silicon is microstructured silicon having a void volume fraction ofabout 0.15 to about 0.75.
 16. A secondary battery comprising theelectrochemical stack of any of claims 1-15.